Acoustic analysis of snoring before and after palatal surgery.

To investigate the effectiveness of palatal surgery for nonapnoeic snoring, 35 patients were block randomised to undergo one of two different palatoplasty procedures. Patients were admitted pre-operatively for audio recording of snoring sound and video recording of sleeping position, and between 1.0 and 4.1 months (mean 2.5) and between 5.9 and 17.5 months (mean 9.7) post-operatively. Sound files, comprising the inspiratory sound of the first 100 snores whilst sleeping in a supine position, were analysed using specifically designed software. Snore duration (s), loudness (dBA), periodicity (%) and energy ratios for the frequency bands 0-200 Hz, 0-250 Hz and 0-400 Hz were calculated. Subjective outcomes were noted. Operation type, body mass index, age, peak nasal inspiratory flow rate, Epworth sleep score and alcohol intake were considered as confounding variables. No patient was cured from snoring. Paired t-test analysis demonstrated statistically significant changes between pre- and early post-operative recordings for snore periodicity and energy ratios in the frequency ranges 0-200 Hz, 0-250 Hz and 0-400 Hz. In conclusion, only the 0-250-Hz energy ratio measurements maintained a statistically significant improvement at the time of the late post-operative recording, despite an obvious drift back to pre-operative levels. No confounding variables were identified. The subjective and objective results correlated poorly. Post-operative changes in the acoustic parameters of snoring sound, following palatal surgery, are demonstrable but short-lived.